It's very complicated the way the Catholic church deals with it. Instead of 15 things that people have to do and some of which people need to continue to do, God requires ONE, and Jesus tells us what that is.
John 3:14-18 And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, that whoever believes in him may have eternal life. “For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. For God did not send his Son into the world to condemn the world, but in order that the world might be saved through him. Whoever believes in him is not condemned, but whoever does not believe is condemned already, because he has not believed in the name of the only Son of God.
John 5:24 Truly, truly, I say to you, whoever hears my word and believes him who sent me has eternal life. He does not come into judgment, but has passed from death to life.
John 6:40 For this is the will of my Father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day.”
John 11:25-26 Jesus said to her, “I am the resurrection and the life. Whoever believes in me, though he die, yet shall he live, and everyone who lives and believes in me shall never die. Do you believe this?”
It's to believe. That's all.
When we do that, we are declared righteous in a judicial pardon of all our sin, and are regenerated, born again as new creatures in Christ.
Sanctification, growing into the likeness of Christ, takes a lifetime, but only happens to those who are already saved, and how we do in becoming sanctified does not affect our justification, which is a done deal.
IOW, we can't lose our salvation due to whatever actions on our part.
Paul warned: "See then the kindness and the severity of God: severity toward those who have fallen, but God’s kindness to you, provided you continue in his kindness; otherwise you too will be cut off" (Rom. 11:22; see also Heb. 10:26–29, 2 Pet. 2:20–21).
All of us are prone to self-deception on this matter. Jesus declared: ‘Not everyone who says to me, "Lord, Lord" shall enter the kingdom of heaven’ (Matt. 7:21)." Even Paul did not claim an infallible assurance of his justification or of his remaining in grace in the future. He wrote, "I am not aware of anything against myself, but I am not thereby justified [Gk., dedikaiomai]." (1 Cor. 4:4). Paul admitted that even he could fall away: "I pummel my body and subdue it, lest after preaching to others I myself should be disqualified" (1 Cor. 9:27).
One can fall from grace through mortal sin, or even fall away from the faith entirely. Jesus said there are those who "believe for a while and in time of temptation fall away" (Luke 8:13). We may have a well-founded hope of being saved; but this is not infallible certitude.
Paul says, "Therefore, my beloved, as you have always obeyed, so now, not only as in my presence but much more in my absence, work out your own salvation with fear and trembling." (Philippians 2:12) Trust in Christ? Yes. Certitude of salvation? No. Our salvation --- says Paul --- is something that remains to be worked out.
I always thought that St. Joan of Arc had an admirable answer when she was asked about her salvation. She said, "I have been saved; I am bring saved; I pray that through God's mercy I will be saved."
Some of the sternest, and, to my mind, most sobering verses in the Gospels are where Jesus tells us solemnly that we will lose our chance of Heaven, of being forgiven of our sins, if we do not forgive:
Matthew 6:15 - "But if you do not forgive others, your Father will not forgive you your sins. ...
Mark 11:26 - "But if you do not forgive, neither will your Father who is in heaven forgive your sins."
Matthew 18:34-35 - "In anger his master handed him over to the jailers to be tortured...This is how my heavenly Father will treat each of you, if you do not forgive your brother from your heart.”
I omitted a WHOLE PARAGRAPH of what I just sent to you. Please kindly check this out. The second paragraph was omitted:
I always thought that St. Joan of Arc had an admirable answer when she was asked about her salvation. She said, "I have been saved; I am bring saved; I pray that through God's mercy I will be saved." I only recently realized that this is just what it says in Holy Scripture: "I am already saved (Rom. 8:24, Eph. 2:5–8), but I’m also being saved (1 Cor. 1:18, 2 Cor. 2:15, Phil. 2:12), and I have the hope that I will be saved (Rom. 5:9–10, 1 Cor. 3:12–15).